Selective electric signaling system



Oct. 11, 1949. E. s. RUTH 2,484,748

SELECTIVE ELECTRiC SIGNALING SYSTEM Filed Feb. 4, 1948 4 Sheets-Sheet 17:22 111 1 A 221 Z 5 A ZIQQ 4 4a 1e INVENTOR HTTORNEYS SELECTIVEELECTRIC SIGNALING SYSTEM Filed Feb. 4, 194a 4 Sheets-Sheet 2 g BUZZERITTORNEY9 221! m; 22a Ill 2'13 224 I 220 218 J INVENTOR B Eda/mu J.ijullz v V Y I I J i m flvuzw aLM (Oct. 11, 1949. E. s. RUTH v 2,484,743

SELECTIVE ELECTRIC SIGNALING SYSTEM I Filed Feb. 4, 1948 4 Sheets-Sheet4 16a INVENTOR f2: {Eda W46! iii/ BY W 7 v.

ATTORNEYS Patented Oct. 11, 1949 2,484,748 SELECTIVE ELECTRIC SIGNALINGSYSTEM- Edward S. Ruth, Norwalk, Conn., assignor to Edwards and Company,Inc., Norwalk, Conn., a corporation of New York Application February 4,1948, Serial No. 6,297

Claims. (Cl. 177353) This invention relates to selective electric sigforindicating at the master station that an individual station has beencalled and for further indicating at the master station the receipt of asignal by an individual at the called station;

Figure 2 is a circuit diagram of a modified 55 master station circuitembodying the useof --a naling system. telephone type of calling dialfor signaling-indi- An object of the invention is to improvesel'ecvidual stations; tive signaling systems such as signaling circuitsFigure 3 is a circuit diagram showing a further for use in apartmenthouses, dormitories, schools 5 modified master station circuit having acommon and the like and for other applications where sereturn signaldevice; and lective signaling is required. Figure 4 illustrates afurther modified master Another object is to provide a selectivesignalstation circuit. ing system requiring a reduced number of signal-In apartment houses, dormitories,--school's and ing conductors. lo anumber of otherlocations there-is frequently A further object is toprovide a signaling sysa need for signaling systems whereby anyone oftem for signaling any one of several stations a number of rooms orstations can be calledfrorn selectively over conductors which are commonto a central location or master station. Thus, in two or more of thestations. dormitories an office or attendants desk is free- A stillfurther object is to provide a selective l5 quently located near theentrance to the building signaling system for calling any one of apluor, in the case of agroup of buildings, in one of rality of stationsfrom a master station and for the buildings of the group. When a visitorcalls signaling the master station from the individual at the attendantsdesk for one of the occupants stati ns. of the dormitory or when atelephone call is re- A specific object of the invention is to provideceived on the house telephone it is usually necesa return call systemfor selective calling stations sary to provide some form of electriccalling syslocated in various rooms in a building or group tem wherebythe attendant can signal the room of buildings from a centralswitchboard or master of one of the occupants and receivea signal backstation. from the occupant indicating that the calling A further objectis to provide a signaling syssignal has been received Buzzer systemshave tem for calling a plurality of individual station-s een p vided nhe past qu r ng a Pair O selectively from a master station and fornotifyconductors leading to each call station or at least ing the masterstation of the receipt of the signal one conductor individual to eachstation. 7 by the individual stations. In apartment houses where noattendant is ther objects are to provide suitable circuits provided a pubu P el fr q and apparatus for carrying out the aforemencated at theentrance to the building to enable tioned objects. a caller to call anyindividual apartment and Other objects of the invention Will be apparentpush buttons are provided in the apartment "for from the followingdescription and accompanyanswering the-call or for unlatching theentrance ing drawings taken in connection with the apdoor to thebuilding. These likewise require at pended claims. least one conductorto each apartment station.

The invention accordingly consists in the fea- The present inventioncontemplates a circuit tures of construction, combination of elements,in which several stations areserved by common and arrangement of partsas will be exemplified ndu or he arran ment in such that inin thestructures to be hereinafter described and dividual Conductors are not qd 1 83 the scope of the application of which will be indi- Station andmeans are provided whe eby any cated in the following claims. stationmay be called or may signal the master In the accompanying drawings inwhich are i n Wi hout efiecti-ng he signaling devices shown by way ofillustration several possibl emassociated with other stations. bodimentsof my invention: The invention makes possible a great reduc- Figure 1 isa circuit diagram of a return n tion in the size of the" master stationswitchboard selective signaling system embodying features of qu d W h st t ater Ope c the invention and comprising a master station ciency,reduced space requirement and greater or switchboard and a plurality ofindividual staportability and convenience of use of the master tions tobe called, together with signaling means station.

According to the preferred method'of practicing the invention rectifiermeans are associated with the individual stations so that certain of thesignaling apparatus at panel.

represent the drawing,

1 according to ing devices associated with uncalled stations or anyinactive parts of the master station during the calling of an individualstation or the calling of the master station from an individual station.

While a preferred embodiment of the invention is described herein, it iscontemplated that considerable variation may be made in the method orprocedure and the construction of parts without departing from thespirit of the invention. In the following description and in the claims,parts will be identified by specific names for convenience, but they areintended to be as generic in their application to similar parts as theart will permit.

Referring to the drawings, Figure 1 shows a selective electric signa1ingsystem suitable for calling the individual rooms of a dormitory orapartments of an apartment house or an aparta ment house roup from acentral point such as an operator-attendant switchboard or a signalingThe portions of the circuit on the left hand'part of the drawing to theleft of the dot and. dash line represent those parts which are locatedat the master station or switchboard and the circuits on the right handpart of the drawing individual room or apartment station circuits. Theconductors shown crossing the dot and dash line are the ones extendingfrom the master station to the various groups of individual stations. Itwill be noted that these are Irelatively few in number and since theymay be of considerable length where the separation of the master stationfrom the call stations is great, the present circuit arrangementrepresents a considerable saving in wiring arrangements over prior artarrangements requiring one or more conductors connecting each individualstation with the master station.

Assuming that the circuit is installed in a dormitory the groups ofstations shown on the right hand part of the drawing may represent thestations located in the individual dormitory rooms. For purposes ofillustration it will be assumed that the lowermost four stations shownin the indicated by reference numerals Nil, 20|, -30| and MN, are thestations located in the first room on the first, second, third and.fourth dormitory floors respectively. The next four stations indicatedby numerals I02, 202, 302 and 402 will then represent the stationslocated respectively in the second room on each floor and so on to theuppermost stations shown, which will represent the signaling stationlocated in room 404; in other words, the fourth room on the fourth floorof the building. While not necessarily so, all of the room stations willgenerally be similarly equipped. Station 404, as illustrated,

buzzer |0, an answering key N and, the present invention, a half-waverectifier |2 such as a plate rectifier of the copper oxide or seleniumtype. The back contact l3, answering key N, buzzer l and rectifier I2are all connected in series between terminals I4 and I5, which representthe terminal connections to the two signal conductors entering the room.An answering conductor I6 is also provided connecting the front contactll of answering key M at the station.

At some or all of the stations it may be desirable also to providevisual indicators such as a drop annunciator in addition to the buzzer.This station 304 is provided, as shown, with a drop annunciator l8 whosewinding is connected in series with buzzer l0.

comprises a When the room is called the buzzer will operate to give anaudible signal,

. individual room stations I push buttons at the same time drop |8 willfan to give visual indication that the room has been called. When theoccupant answers drop |8 can be manually reset.

The master station comprises a switchboard provided with a series oftelephone jacks comprising sleeve contacts such as 2|, 22, 23 and 24 andtip contacts 3|, 32, 33 and 34. The switchboard is also provided with aseries of push but tons such as push buttons 2, 3 and 4.

Switchboard lamps 4|, 42, 43 and 44 are associated respectively with thetelephone jacks. An individual lamp control relay is associated witheach jack and is provided with relay contacts 8|, 82, 83 and 84respectively for closing the lamp energizing circuits 9|, 92, 93 and 94respectively in response to the energization of operating windings 5|,52, 53 and 54 respectively of the relays. A lamp energizing transformer25 has its secondary winding connected at one end to common conductor 25leading to all of the lamps and at the other end to common conductor 21leading to one of the contacts of each of contact pairs 8| to 84, theother contact of each pair being connected respectively to theindividual lamp energizing circuits 9| to 94 respectively. Relay resetwindings 6|, respectively are associated with respective lamp controlrelays for opening the lamp circuits after they have been closed by theoperating reset windings. Each of the reset windings has connected inseries with it a half-way rectifier, namely rectifier H to 14respectively. Each of the reset windings are connected between commonconductor 26 and signaling conductors M2, I I3 and I I4 respectivelyleading respectively to the individua1 room station groups having thesame last digit. For example, signaling conductor ||4 leads to terminall4 and hence to keys H and I04 to 404 inclusive.

A second power supply transformer 28 for supplying signaling current hasits secondary winding connected between one terminal of each of 2, 3 and4 and. the sleeve contact 29 of the switchboard plug. The tip contact 30of the plug is connected by conductor 35 through normally-open pushbutton switch 36 to common conductor 21. Push button 36 is located atthe master station for the purpose of resetting the signal lamp relaysin case a called station does not answer.

Push buttons to to signaling conductors la, 2a, tively which lead to allof the respective floor.

The operation as follows:

When the operator at the master station wishes to call an individualroom station, say room 404, she inserts the switchboard plug in to thejack associated with all of the rooms ending in the digit 4, namely jack24 in the present example.

4 respectively are connected 3a and 4a respecroom stations on a of thesystem can be carried out She then pushes thev push buttons associatedwith the floor desired. In the present instance. Push button 4.

62, 63 and 64 sleeve 24 of the switchplug and conductor 37 to theopposite terminal of the secondary winding of transformer 28. Signalingcurrent through this circuit operates buzzer II] to give an audiblesignal at individual room station 494 and energizes relay winding 54 toclose relay contacts 84 to light signal lamp 44. The lamp energizingcircuit extends from the sec ondary winding of transformer to conductor26, lamp 44, conductor 94, rela contacts 34, and common conductor 27back to transformer 25. This gives a visual signal or indication at theswitchboard that the room has been called.

When the occupant of the room hears the buzzer he is supposed to answerby pressing key I I momentarily. As key II is pressed a reset circuit isclosed to extinguish signal lamp 44 as follows:

From the right hand end of transformer 25 through common conductor I5,front contact I! of key II, key I I, the individual room circuit toterminal I4, conductor H4, rectifier l4, relay reset winding 64, commonconductor 26 back to the left hand end of the secondary winding oftransformer 25. This energizes winding 54 to open relay contacts 84 andthereby extinguish the lamp.

Should the room occupant fail to answer the operator at the masterstation can extinguish the lamp simply by pressing push button 36 whichcloses an operating circuit for reset winding 64 from transformer 25through conductor 35, plug tip 3!], jack contact 34, rectifier l4,winding 64 and common conductor 26 back to the transformer.

The advantages and function of the rectifiers variously located in thecircuit will now be apparent. First as to rectifiers individual roomstation; if room station 494 is being called current is supplied fromthe secondary winding of transformer 28 through push button 4 andconductor 4a to the room station. However, conductor 4a is alsoconnected to all other stations on the fourth floor, such as stations453i, 402, and 403 and hence one side of each of these room stationcircuits is bridged together. Similarly for stations on each of theother floors. However, certain groups of stations are also bridgedtogether in another way as by conductors I I I, II2, I I3 and II 4respectively, each of which is connected to a group of stations endingin the same digit. Without the rectifiers I2 in the circuit it wouldthus be possible for signaling current pasing through push button 4 andconductor to find its way back to the transformer, not only throughstation 404 which is intended to be called but also through severalother paths such as follows:

From conductor 4a through station 403 and via the portion of conductorII3 which connects the stations ending in digit 3 together, then throughstations I03, 203 and 303 to conductors Ia, 2a and 3a respectively. Fromthese conductors the current can find a, ready return path totransformer 28 through stations I54, 204 and 304 respectively, conductorII4, relay winding 54, sleeve contact 24, plug sleeve 29, the plug beingat this time inserted in sleeve 24, and conductor 3? back to transformer28. However, with rectifiers I2 in each station circuit, each rectifierbeing directed to pass current through its station in the samedirection, such a return path is blocked. Thus, while current could findits way via conductor 4a through station 403 to conductor H3 it would beblocked from finding a return path to the transformer since, at thistime, the switchboard plug is not connected to sleeve 23 and therectifiers I2 at individual stations I05, 253 and-303 are biased I2located at each shown in Figure-2, the

6 in the direction which prevent current flow from conductor I I3through the stations to conductors Ia, 2a and 3:1.

It will thus be evident, that by use of rectifiers I2 at the individualstations, a large number of room stations can be called from the centralswitchboard or master station, over a small number of conductors. In theexample illustrated only'four floors and four stations per floor areindicated. However, it will be apparent that both the number of floorsand the number of stations per floor can be increased or reduced. Ingeneral, one additional conductor leading from the master station isrequired for each additional floor being served by the switchboard andone additional conductor is required to be added for each additionalgroup of room stations ending in the same digit. The advantages thusbecome more evident when a large building or a large number of stationsare served.

The function of rectifiers II, 12, 13 and 74, located at the masterstation, is to prevent another condition in which room stations might befortuitousl called. For'example, in the absence of rectifier 14 whenstation 4041s called the signaling current would also find a path forcalling station 403 from push button 4 through conductor 4a, station403, conductor H3, rectifier l3, winding 63, winding 64, conductor H4,winding 54, sleeve 24, plug sleeve contact 29, and conductor 37: backthrough transformer 23 to the push button. The rectifiers II to I4prevent such sneak circuits which would interfere with the properfunctioning of the system.

Figure 2 is a circuit diagram of a modified signaling system in whichthe stations are called by use of a telephone type dial in combinationwith a series of push buttons. The figure shows only the master stationsince the individual room station circuits are similar to thoseillustrated in Figure 1. Circuit conductors and circuit elements havebeen given the same reference numerals where they are similar infunction and relative location in the circuit.

In addition to current supply transformers 25 and 23 a third transformer2I2 is provided which current from full-wave rectifier 2I3 to dial 2Mand winding 2 I8 of stepping switch 7 2I9 connects one contact of thedial to the rectifier and conductor 220 connects the other outputterminal of the rectifier to winding 2IB of the stepping switch. I Thedial pilot lamp 2I5 is connected between conof the stepping switch.Conductor 228 connects dial 2M to stepping winding 2 I 8.

If desired, for convenience, dial 2I4, pilot light 2I5, reset key '2I6,floor push buttons I, 2, 3 and 4, switchboard lamps 4|, 42, 43 and 44,resetting push button 35 and a buzzer 2II may all be installed at theoperators location as indicated by the dashed rectangular 229, whilestepping switch 2i! the relays having windings 5i to 54, current supplytransformers 25, 28 and 2I2, and rectifier MS may be located in anotherspace such as in a closet or in the basement of the building.

In operation of the dial system shown in Figure 2, assuming the operatorwishes to call station 424 (Figure 1) from the master station operatorwill simply dial another position.

the. station digit on dial 2I-4, namely the numeral 4. Operation of thedial effects closure of the dial contacts momentarily four times insequence. Each time the dial contacts are closed an energization circuitfor stepping relay winding 2 I 8 is closed as follows:

From rectifier 2I3 via conductor 2.I9, dial 2I4, conductor 228, winding218 and conductor 220 back to the rectifier. Energization of the winding2I8 causes it to step contact arms 22l, 222, 223 and 224 ahead oneposition for each energization of the winding, the arms engagingcooperating contacts arranged in an are around them as they are advancedeach step. Thus, arm 22E will be advanced to the fifth contact to closea circuit from transformer 28 via conductor 31, contact arm 22I,conductor 234, relay winding '54, conductor H4 to all room stationsending in the digit 4. When push button 4 is pressed, after this circuithas been established, the circuit is completed through room station.404, conductor 4a, push button 4, master station buzzer 2| I andconductor 2 I ll back to transformer 28, thereby operating the buzzer atroom station 434 and simultaneously operating the buzzer at the masterstation to indicate to the operator that the station is being called.Relay winding 54 is also energized and operates its armature to closecontacts 84, thus completing the circuit for signal lamp 44 giving avisual indication to the operator that a station ending in the digit 4is being called.

When the person at station 434 answers by operating answering key II acircuit is completed for extinguishing lamp 44 as follows:

From the secondary winding of transformer 25 via conductor I3 throughroom station 404, then via conductor II4, rectifier 14, winding 64 andconductor 25 back to transformer 25.

Winding 64 thereupon opens contact 84 to extinguish the lamp.

Should no answer be received from the called station the operator canextinguish lamp 44 by momentarily pressing push button 36 which closes acircuit from transformer 25 via conductor i3, push button 36, conductor235, selector switch arm 222, conductor 23B, rectifier 14, Winding 64and conductor 26 back to the transformer. Contact arm 222, in the secondbank of the selector switch, serves the purpose of connecting pushbutton 36 to the reset winding of any digit dialed by the operator sothat the indicating lamps may be selectivel extinguished before callinga second station. But, it also is possible for the operator to call asecond station while she is awaiting a response from the first stationby later redialling the first station for the purpose of extinguishingthe first station signal by. push button 35 if a response is notreceived from that station.

In order to restore selector switch 2I'I to its normal or home positionreset key 2I6 is provided. Thus, when the selector switch arms are onany selected station position the switch may be returned to normal bymomentarily pressing push button 2E6. This closes a stepping circuitthrough interrupter contacts 225 of the stepping switch and switch arm223 through operating winding 2I8. Contacts 225 are opened by the switchmechanism switch arms, thus allowing the stepping lever controlled bywinding 2; to fall back. However, in doing so the lever closes contacts225 to reenergize winding 2I8 and to advance the switch Hence, whileresetkey2l6 is at each station position of the from transformer 28,during the calling of an inclosed the switch will automatically steparound until it is returned to home position in which all contact armcircuits are opened and the winding H8 is de-energized.

Contact arms 22l, 222 and 224 are non-brid ing with respect to theirassociated contacts. That is, the circuit through the contact arms ismomentarily opened while the arms are being transferred from one contactto the next succeeding contact of the ban Contact arm 223, however, ispreferably of the bridging type so that the circuit is entirely undercontrol of interrupter contacts 225 as long as reset key 2H5 is closedand the switch is not at home position.

Contact arm 224 closes the circuit at each digit position for pilot lamp2l5 so that when a digit is dialed a pilot lamp flashes momentarily asthe switch advances each position. This indicates to the operator thatthe selector switch is operating properly in response to the dial.

It is obvious that where the number of room stations on a floor exceedthe number of digits on the calling dial the selector switch can be intwo or more stages. The operator will then dial one number to select thetens digit thereby setting up a first rotary switch to a contact leadingto a second rotary switch. The operator then dials the units digit toset up the selected position on the second switch. The two switchestogether then will complete the circuit to the room station selectedwhen the desired floor key is pressed.

Figure 3 illustrates a further, and more simplified master stationcircuit for calling individual room stations similar to those shown inFigure 1. Such a circuit is useful, for example, at an unattendedlocation such as the entrance to an apartment building where an operatoris not provided. The master station comprises a switchboard having aseries of jacks such as jacks 32I, 322, 323 and 324 connected toconductor III, H2, H3 and H4 respectively leading to the room stations.Push buttons corresponding to each floor are also provided such as pushbuttons I, 2, 3 and 4 for closing circuits over conductors Ia, to 4arespectively. The switchboard plug comprises a single sleeve contact 329for engaging the sleeves of jacks 32I and the like.

An answering buzzer 3I I is also provided which is connected throughrectifiers 33!, 332, 333 and 334 respectively to conductors III, H2, H3and H4 respectively. Transformers 25 and 28 provide power supply forsignaling current.

When a person wishes to call a room station he places the switchboardplug in the jack whose identification number ends in the digit of thecall station desired and pushes the button corresponding to the floor onwhich the station is located. Thus, if station 404 is desired the plugis placed in jack 324 and push button 4 is pressed. This closes asignaling circuit from transformer 28 via conductor 31, plug contact329, jack 324, conductor H4, room station 434, conductor 40., pushbutton 4 and conductor 3H1 to transformer 28. In this system the roomstation is called but no indication is given by the switchboard duringcalling. However, when the person at the room station answers, a circuitis completed for operating answering buzzer 3lI from transformer 25 viaconductor I6, room station 464, conductor H4, rectifier 334, buzzer 3Hand conductor 26 back to transformer 25.

Rectifier 33I et al. prevent signaling current gal-84,3248

dividual station, from passing over conductors leading. to other groupsof stations which might otherwise be fortuitously called. In thevabsence of these rectifiers when station 404-is being called a circuitwould also be closed for calling station 403- from jack 324 overconductor 3|? to jack 323 and over conductor H3 to the room station.Similar circuits would also be closed for calling allother stations onthe fourth floor. However, rectifiers 3-3l to 334 are so biased thatcurrent sent over one conductor cannot find its way to any of theothers.

Figure 41s a circuit diagram of a further modified system. This systemis generally similar to the system illustrated in Figure l and theoperation is substantially the same. However, in this system therectifiers l2 are not located at the individual room stations but aregrouped together in. a power unit which may be located at anyconvenient. location in individual. room stations are located, such asin the basement or a service room. The power unit indicated by areference numeral 4l0 may include, in addition to the banks ofrectifiers l2,

the transformer unit comprising transformers 25 and 28'.

The master station, indicated by reference numeral 4| I may be locatedat a point remote from the powerunit and from the room stations, suchas; in. another building. The number of conductors connecting the masterstation with the power unit are relatively small, by virtue of the useof the rectifiers arranged according to the present invention.

A single room station 404 is illustrated in Figure 4, the other room.stations being similar and the connecting circuits being readilyapparent from the diagram. Referring to room station 404 it will benoted that it is similar to the room station previously described inconnection with Figure 1 with the exception that rectifier I2 is notlocated at the station position. The signalling push button 4 overconanswering key N at the room station, is indivdual to station 404 andextends to one of the rectifiers l2, located in the power conductor H4which is common to all stations ending in the digit 4 to the masterstation. Answering conductor 404a extending from answering contact [1 ofkey II is connected to a conductor |6a which is common to all stationson the fourth floor. Conductor lSa, in common with similar conductorsltb, I60 and the like leading from the other floors are all connected tothe return conductor It in the power unit.

The system of Figure 4 has the advantage of simplified room stations andthe location of the rectifiers and transformers in a service room wherethey can be readily checked and serviced at any time without disturbingthe room occu pants. This is of particular value in hospitals andsimilar institutions.

Since the operation of the system of Figure 4 is similar to that ofFigure 1, it is not believed necessary to describe it in further detail.

It will be seen that a selective electric signaling system has beenprovided in accordance with the present invention in which the number ofconductors required have been greatly reduced Without limiting thefunctioning of the system.

One of the greatest advantages of the system unit 410 and hence over a:

the building where the resides in the greatly reduced switchboardarearequired. In the past such switchboards have often required so muchspace that itv was necessary for the operator to get up from her seat.and walk to the desired switchboard location to insert the calling plug,often being required to, reach way above her head for high positions.This greatly reduced the number of calls, an operator could handleefiiciently. and thereby produced resultant delays and unsatisfactoryservice. The bulk of wires leading to the switchboard also occupiedexcessive valuable space and complicated the problem of installing thewiring and switchboard, as well as their maintenance.

Prior master stations have often required a, switchboard area, eightfeethigh and eight feet or more wide to serve 1000 rooms due to thebulk, of wire terminals behind the board and the area of the equipmenton the face of the board. A cabinet embodying the master station fora1000- room system arranged according to the present invention need beonly 6 inches high and loinches. wide. Where the dial system in used itmay be even smaller.

It is thus possible, by providing a fiexiblecable. carrying theconductors leading to. the master station, to mount it on a portablestand or cart. which can be placed at the location most con.- Venientfor the reach of the operator. Thus itv may be mounted beside an outsidetelephone switchboard so as to be readily accessible by. the regulartelephone operator. When desired it may be moved beside a desk foroperation by a secretary during less busy periods.

It is also contemplated that the master station may be incorporated in anarrow switchboard of. the same height as a conventional outgoing-teleephone switchboard so as to be placed beside the telephone switchboardand in effect, be made a. part of it.

Moreover it is possible with the system to locate the master station ata remote point while achieving economy of wiring. The servicing of thesystem is also simplified by the present invention.

While the present invention, as to its objects and advantages, has beendescribed herein as carried out in specific embodiments thereof, it isnot desired to be limited thereby but it is intended to cover theinvention broadly within the spirit and scope of the appended claims.

What is claimed is:

1. A selective electric signaling system comprising in combination aplurality of groups of electric signaling devices, a source of electriccurrent, a first series of conductors, each conductor of which isindividual to one of said groups, a second series of conductors, each ofwhich is connected to at least one of said devices in each group, eachof said signaling devices being connected between the member of thefirst series of conductors which is individual to its respective groupand a member of said second series of conductors, switching devices forselectively connecting one terminal of said source to any one of saidfirst series of conductors and for connecting the other terminal of saidsource to any one of said second series of conductors, a rectifierconnected in series with each of said signaling devices, anelectroresponsive device connected in series with each member of one ofsaid series of conductors, a call-indicating signal device controlled byeach of said electroresponsive devices, a second electro-responsivedevice connected to each member of said one series of conductors, thecall-indicating signal being controlled by each said first-mentionedelectroresponsive devices by the corresponding second electroresponsivedevice to return the signal to normal, and a plurality of energizingcircuits for each of said second devices, each energizing circuitincluding a source of electric energy, manually-controlled contacts atan individual station and at one of said series of conductors.

2. A selective electric signaling system comprising a master station anda plurality of groups of room-call stations, an electric signalingdevice at each of said room-call stations, a rectifier in series witheach of said signaling devices, a first series of conductors eachconnecting said master station with one terminal of the signalingdevices at all of the room-call stations of one of said groups, a secondseries of conductors each connecting said master station with the otherterminal of the signaling devices at one of said room-call stations ineach of said groups, a source of electric energy, manually-controlledswitching devices at said master station for connecting one terminal ofsaid source to any selected member of said first series of conductorsand for connecting the other terminal of said source to any selectedmember of said second series of conductors, a plurality ofcall-indicating signal devices located at said master station, andelectroresponsive devices connected in series with each of one of saidseries of conductors, said call-indicating signal devices beingrespectively controlled by said electroresponsive devices to indicatethe sending of a calling signal from said master station, a secondseries of electroresponsive devices, said second electroresponsivedevices restorin said call-indicating signal devices respectively tonon-indicating condition, a manual signaling switch at each of saidroom-call stations, 2. second source of electric energy, each of saidmanual signaling switches being connected between one terminal of saidsecond source and a member of said one series of conductors, said secondelectroresponsive devices being connected respectively betweenmembers ofsaid one series of conductors and the other terminal of said secondsource of energy, and a rectifier in series with each of saidseconddevices.

3. A selective electric signaling system comprising a master station anda plurality of groups of room-call stations, an audible electric signaling device at each of said room stations, a rectifier in series witheach of said signaling devices between the terminals of said roomstations, a first series of conductors each connecting said masterstation with a first terminal of all of the room-call stations of one ofsaid groups, a second series of conductors, each connectin said masterstation with a second terminal of one of said room stations in each ofsaid groups, a source of alternating current energy, a switchboard plughaving a contact connected to one terminal of said source, a pluralityof switchboard jacks, each having a contact for cooperative engagementwith said plug contact, said jack contacts being connected respectivelyto said first conductors, a plurality of push button switches eachconnected between the other terminal of said source and one of saidsecond conductors, said system also comprising a series of relays eachhaving a first winding for closing a pair of relay contacts and a secondwinding for opening said contacts, a series of switchboard lamps andenergizing circuits therefor controlled respectively by said relaycontacts, the first of said relay windings being connected respectivelyin series with said first series of conductors, a rectifier in serieswith the sound of each of said; windings, a second source of alternatingcurrent energy, each of said series combination of second windings andrectifier being connected between the first terminal of said secondsource and the conductor to which its associated first winding isconnected, an answering switch at each of said room stations having acommon contact being connected to said first terminal of said roomstation and said back contact being connected to the second terminal ofsaid station through said audible signaling device, said front contactbeing connected to the second terminal of said second source ofalternating current energy.

4. A selective electric signaling system comprising a master station anda plurality of groups of room-call stations, an audible electricsignaling device at each of said room stations, a rectifier in serieswith each of said signaling devices be tween the terminals of said roomstations, a first. series of conductors each connecting saidmasterstation with a first terminal of all of the roomcall stations ofone of said groups, a second series of conductors, each connecting saidmaster station with a second terminal of one of said room stations ineach of said groups, a source of alternating current energy, aswitchboard plug having a contact connected to one terminal of saidsource, a plurality of switchboard jacks, each having a contact forcooperative engagement with said plug contact, said jack contacts beingconnected respectively to said first conductors, a plurality of pushbutton switches each connected between the other terminal of said sourceand one of said second conductors, said system also comprising areturn-call check signal device at said master station and a secondsource of alterhating current energy connected in series there with, anda series of rectifiers, each of said rectifiers being connected betweenone of said jack contacts and one terminal of the series arrangement ofsaid return-call signal and said second source of alternating currentenergy, an answering switch at each of said room stations having acommon contact and a back and a front contact, said common contact beingconnected to said first terminal of said room stations and said backcontact being connected to the second terminal of said station throughsaid audible signaling device, said front contact being connected to thesecond terminal of said series arrangement of return-call signal andsecond source of alternating current energy.

5. A selective electric signaling system comprising a master station anda plurality of groups oi room-call stations, an audible electricsignaling device at each of said room stations and a rectifier in serieswith each of said signalling devices between the terminals of said roomstation, a first series of conductors, each connecting said masterstation with a first terminal of all of the room-call stations of one ofsaid groups, a second series of conductors, each connecting said masterstation with a second terminal of one of said room stations in each ofsaid groups, a source of alternating current energy, a stepping switchand a manual dial circuit for advancing the same, the stepping switchhaving a movable contact arm connected to one terminal of said sourceand a series of stationary contacts for cooperation therewith andconnected respectively to said first conductors, a plurality of pushbutton switches, each connected between the other terminal of saidsource and one of said second conductors, a series 13 of relays, eachhaving a first winding for closing a pair of relay contacts and a secondwinding for opening said contacts, a series of indicating lamps andenergizing circuits therefor controlled respectively by said relaycontacts, the first of said relay windings being connected respectivelyin series with said first series of conductors, a rectifier in serieswith the second of each of said Windings, a second source of alternatingcurrent energy, each of said series combination of second Winding andrectifier being connected between a first terminal of said second sourceof alternating current energy and the conductors to which its associatedfirst winding is connected, an answering switch at each of said roomstations having a common contact and a back and front contact, saidcommon contact being connected to said first terminal of said roomstation and said back contact being connected to the second terminal ofsaid station through said audible signaling device,

said front contact being connected to the second terminal of said secondsource of alternating current energy.

EDWARD S. RUTH.

REFERENCES CITED The following references file of this patent:

UNITED STATES PATENTS are of record in the

